ИСТИНА

The ATPase activity of H+-FOF1-ATP synthase can be regulated in several ways, but the most common of them is inhibition by MgADP. It is known for all studied FOF1 complexes that MgADP bound in a catalytic site in the absence of phosphate may cause enzyme inactivation instead of being released and replaced by new MgATP. The degree of this inhibition varies greatly between different organisms: the inhibition is strong in chloroplast FOF1 and enzymes of some bacteria (Bacillus PS3, Bacillus subtilis), but in FOF1 of Escherichia coli it is much weaker. It has been reported previously [1] that a point mutation Gln259Leu in the beta subunit of Bacillus PS3 FOF1 noticeably relieves its strong MgADP inhibition. In this work, we inserted the same mutation in B. subtilis. MgADP inhibition in our mutant FOF1 also weakened significantly in comparison to the wild-type enzyme. The mutant was capable of ATP-driven proton pumping and was sensitive to azide like the wild type. The initial ATPase activity levels of the mutant and of the wild-type FOF1 complexes were comparable at room temperature and at 37 °C, but the mutant enzyme has demonstrated sensitivity to cold temperatures. The living cells of the mutant strain also were not resistant to cold. To clarify the physiological role of MgADP inhibition in B. subtilis, we also compared wild-type and mutant strains in competition growth experiments under different conditions. [1] B. A. Feniouk, C. Wakabayashi, T. Suzuki, M. Yoshida, A point mutation, betaGln259Leu, relieves MgADP inhibition in Bacillus PS3 ATP synthase, BBA - Bioenergetics, 1817 (2012) S22.